This Program Project brings together five researchers with very different expertise and experimental capabilities to work together on elucidating the underlying mechanisms of S0D1-linked familial amyotrophic lateral sclerosis (fALS) pathogenesis. It is well established that S0D1 multimers and larger aggregates are associated with disease but the toxic species and in vivo mechanism remain unknown. The overall goals of this proposal are to gain an extensive understanding of the role of aggregation in disease, to characterize further the biochemical properties associated with mutant S0D1 and its aggregation, to uncover clues about the initiation and progression of disease, to exploit this understanding to develop targeted blockers of multimerization. The PPG collaboration will encompass five primary investigators with four projects and a technical Core. Projects 1 (Dr. Joan Valentine) and 4 (Dr. David Eisenberg) will take an in vitro structural and biophysical approach to studying the mechanism of S0D1 multimerization and the structures of the multimers, with the goals of understanding the mechanism(s) of multimerization and designing inhibitors of aggregation. Project 2 (Dr. Martina Wiedau-Pazos) will use stem cell-derived motor neurons and glia and project 3 (Dr. David Borchelt) will use a mouse,and cell culture models to probe the toxicity of multimers and to characterize the changes in mutant S0D1 that lead toward disease. A particular emphasis on the latter project will be toward in vivo metal loading as it pertains to S0D1 stability, and metal homeostasis as it pertains toward cellular toxicity. Core A (Dr. Julian Whitelegge) will serve as the backbone of these investigations by providing and maintaining the necessary instrumentation and data delivery. Disease models from projects 2 and 3 will be used to test the efficacy of inhibitors from projects 1 and 4. Finally, ALS tissue will be used as a source to validate the findings and test new hypotheses.